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Uses and corrosion of Zr-Alloys Zr-alloys used as cladding materials of the fuel rods. In service environments oxidation occurs limiting their service life. OXIDE METAL

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Uses and corrosion of Zr-Alloys Zr-alloys used as cladding materials of the fuel rods. In service environments oxidation occurs limiting their service life. Better understanding of the corrosion mechanisms could lead to improvement of the burn up efficiency. Residual stresses in the oxide are believed to play key role on the corrosion properties of the material.

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Origin of stresses Transformation strain. Transformation of Zr-ZrO 2 is accompanied by volume dilatation. (volume of ZrO 2 is 1.56 times greater than Zr) How do stresses affect oxidation? The tetragonal phase can be stress stabilised As oxidation proceeds stresses might be reduced in the oxide away from the interface, which could lead to t m phase transformation This phase transformation is associated with a further volume increase ─ cracks─ acceleration of corrosion kinetics Stresses in Zr-alloys oxides

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Conclusions A stress profile exists through oxide thickness - maximum compressive stresses near the O/M interface stress decay away from interface may enable tetragonal to monoclinic phase transformation. Stress reduces with oxidation time. A stress profile may be produced by creep of substrate – however the shape of the measured profile does not match the profiles predicted by substrate creep alone. Stress profile affected by other factors such as cracks between the oxide layers.